How Digital Rights Management Works

Digital rights management is a far-reaching term that refers to any scheme that controls access to copyrighted material using technological means. In essence, DRM removes usage control from the person in possession of digital content and puts it in the hands of a computer program. The applications and methods are endless -- here are just a few examples of digital rights management:

A company sets its servers to block the forwarding of sensitive e-mail.

An e-book server restricts access to, copying of and printing of material based on constraints set by the copyright holder of the content.

A movie studio includes software on its DVDs that limits the number of copies a user can make to two.

A music label releases titles on a type of CD that includes bits of information intended to confuse ripping software.

While many consumers see DRM methods as overly restrictive -- especially those methods employed by the movie and music industries -- digital rights management is nonetheless trying to solve a legitimate problem. The distribution of digital content over the Internet via file-sharing networks has made traditional copyright law obsolete in practice. Every time someone downloads an MP3 file of a copyrighted song from a free file-sharing network instead of buying the CD, the music label that owns the copyright and the artist who created the song lose money. In the case of the movie industry, some estimates place revenue losses from illegal distribution of DVD content at around $5 billion a year. The nature of the Internet makes it impractical to try to sue every person who breaks the law in this way, so companies are trying to regain control of distribution by making it technologically impossible for consumers to make digital copies.

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The problem is that when you buy a DVD, it's perfectly legal for you to make a copy of it for your own use. This is the gist of the fair use doctrine in copyright law -- there are certain situations that negate copyright protection in favor of the content user, including copying protected material for personal use and copying anything in the public domain for any use. Most digital rights management schemes cannot take fair use into account, because a computer program cannot make subjective decisions.

Before we get further into the DRM controversy, let's take a step back and find out what a DRM scheme entails from a programming standpoint.

DRM History

DRM is not a new thing -- many of those old floppy disks were copy-protected. Manufacturers wrote them using special drives that a typical consumer drive couldn't mimic. Some required that a piece of hardware be connected to an I/O port on the computer for the software to run at all.